when should you add a message queue between services. like, when does it actually make sense to do that

So, I've been thinking a lot about how we're handling communication between our microservices, especially since we keep adding more. Right now, we're just doing direct HTTP calls, and honestly, it's feeling pretty fragile. I'm wondering when it actually makes sense to bring in something like RabbitMQ or Kafka. Like, is it when we hit a certain number of services, or when requests start timing out a lot? Or is there some other thing you look for? Would love to hear what you all have experienced and what makes you pull the trigger on a message queue.